It is known that containers can be sealed with metal caps that are folded or crimped upon and around the container opening.
There is a problem connected with the removal of such seals (closures or caps), especially seals for milk, cocoa or juice bottles, that consist of a thin metal foil, and that are penetrated by a drinking straw.
For recycling purposes, the seal parts, that are still present on empty bottles, must be removed completely before the bottles are reused. For this purpose, the bottles, for example, are run through rotating brushes that scratch the seal remnants off the bottle opening; in this procedure, seal materials, such as aluminum or a light-metal alloy, or a glass, are partly pulverized from the container and metal dust or glass splinters are released; this causes considerable contamination of the filling systems. Besides, the bottle necks are scratched and damaged by the rotating brushes so that it is more difficult to put a tight new seal on the bottles, as a result of which the reusability cycle of those bottles is cut short. Besides, bottles with scratches incline toward rupture.